R. J. Gutiérrez

Understanding and managing conservation conflicts.

Conservation conflicts are increasing and need to be managed to minimise negative impacts on biodiversity, human livelihoods, and human well-being. Here, we explore strategies and case studies that highlight the long-term, dynamic nature of conflicts and the challenges to their management. Conflict management requires parties to recognise problems as shared ones, and engage with clear goals, a transparent evidence base, and an awareness of trade-offs. We hypothesise that conservation outcomes will be less durable when conservationists assert their interests to the detriment of others. Effective conflict management and long-term conservation benefit will be enhanced by better integration of the underpinning social context with the material impacts and evaluation of the efficacy of alternative conflict management approaches.

Modeling species occurrence dynamics with multiple states and imperfect detection

Recent extensions of occupancy modeling have focused not only on the distribution of species over space, but also on additional state variables (e.g., reproducing or not, with or without disease organisms, relative abundance categories) that provide extra information about occupied sites. These biologist-driven extensions are characterized by ambiguity in both species presence and correct state classification, caused by imperfect detection. We first show the relationships between independently published approaches to the modeling of multistate occupancy. We then extend the pattern-based modeling to the case of sampling over multiple seasons or years in order to estimate state transition probabilities associated with system dynamics. The methodology and its potential for addressing relevant ecological questions are demonstrated using both maximum likelihood (occupancy and successful reproduction dynamics of California Spotted Owl) and Markov chain Monte Carlo estimation approaches (changes in relative abundance of green frogs in Maryland). Just as multistate capture-recapture modeling has revolutionized the study of individual marked animals, we believe that multistate occupancy modeling will dramatically increase our ability to address interesting questions about ecological processes underlying population-level dynamics.

OCCUPANCY ESTIMATION AND MODELING WITH MULTIPLE STATES AND STATE UNCERTAINTY

The distribution of a species over space is of central interest in ecology, but species occurrence does not provide all of the information needed to characterize either the well-being of a population or the suitability of occupied habitat. Recent methodological development has focused on drawing inferences about species occurrence in the face of imperfect detection. Here we extend those methods by characterizing occupied locations by some additional state variable (e.g., as producing young or not). Our modeling approach deals with both detection probabilities <1 and uncertainty in state classification. We then use the approach with occupancy and reproductive rate data from California Spotted Owls (Strix occidentalis occidentalis) collected in the central Sierra Nevada during the breeding season of 2004 to illustrate the utility of the modeling approach. Estimates of owl reproductive rate were larger than naïve estimates, indicating the importance of appropriately accounting for uncertainty in detection and state classification.

STATUS AND TRENDS IN DEMOGRAPHY OF NORTHERN SPOTTED OWLS, 1985-2003

Abstract We analyzed demographic data from northern spotted owls (Strix occidentalis caurina) from 14 study areas in Washington, Oregon, and California for 1985–2003. The purpose of our analyses was to provide an assessment of the status and trends of northern spotted owl populations throughout most of their geographic range. The 14 study areas made up approximately 12% of the range of the subspecies and included federal, tribal, private, and mixed federal and private lands. The study areas also included all the major forest types that the subspecies inhabits. The analyses followed rigorous protocols that were developed a priori and were the result of extensive discussions and consensus among the authors. Our primary objectives were to estimate fecundity, apparent survival (φ), and annual rate of population change (λ) and to determine if there were any temporal trends in these population parameters. In addition to analyses of data from individual study areas, we conducted 2 meta-analyses on each demographic parameter. One meta-analysis was conducted on all 14 areas, and the other was restricted to the 8 areas that constituted the Effectiveness Monitoring Plan for northern spotted owls under the Northwest Forest Plan. The average number of years of reproductive data per study area was 14 (range = 5–19), and the average number of recapture occasions per study area was 13 (range = 4–18). Only 1 study area had <12 years of data. Our results were based on 32,054 captures and resightings of 11,432 banded individuals for estimation of survival and 10,902 instances in which we documented the number of young produced by territorial females. The number of young fledged (NYF) per territorial female was analyzed by testing a suite of a priori models that included (1) effects of age, (2) linear or quadratic time trends, (3) presence of barred owls (Strix varia) in spotted owl territories, and (4) an even-odd year effect. The NYF varied among years on most study areas with a biennial cycle of high reproduction in even-numbered years and low reproduction in odd-numbered years. These cyclic fluctuations did not occur on all study areas, and the even–odd year effect waned during the last 5 years of the study. Fecundity was highest for adults (x̄ = 0.372, SE = 0.029), lower for 2-year-olds (x̄ = 0.208, SE = 0.032), and very low for 1-year-olds (x̄ = 0.074, SE = 0.029). Fecundity was stable over time for 6 areas (Rainier, Olympic, Warm Springs, H. J. Andrews, Klamath, and Marin), declining for 6 areas (Wenatchee, Cle Elum, Oregon Coast Range, Southern Oregon Cascades, Northwest California, and Simpson), and slightly increasing for 2 areas (Tyee, Hoopa). We found little association between NYF and the proportion of northern spotted owl territories where barred owls were detected, although results were suggestive of a negative effect of barred owls on the Wenatchee and Olympic study areas. The meta-analysis on fecundity indicated substantial annual variability with no increasing or decreasing trends. Fecundity was highest in the mixed-conifer region of eastern Washington (x̄ = 0.560, SE = 0.041) and lowest in the Douglas-fir (Pseudotsuga menziesii) region of the Oregon coast (x̄ = 0.306, SE = 0.039). We used Cormack–Jolly–Seber open population models and Program MARK to estimate apparent survival rates of owls >1 year old. We found no differences in apparent survival rates between sexes except for 1 area (Marin), which had only 6 years of data. Estimates of apparent survival from individual study areas indicated that there were differences among age classes with adults generally having higher survival than 1- and 2-year-olds. Apparent survival rates ranged from 0.750 (SE = 0.026) to 0.886 (SE = 0.010) for adults, 0.626 (SE = 0.073) to 0.886 (SE = 0.010) for 2-year-olds, and 0.415 (SE = 0.111) to 0.860 (SE = 0.017) for 1-year-olds. These estimates were comparable to survival rates from previous studies on the subspecies. We found evidence for negative time trends in survival rates on 5 study areas (Wenatchee, Cle Elum, Rainier, Olympic, and Northwest California) and no trends in survival on the remaining areas. There was evidence for negative effects of barred owls on apparent survival on 3 study areas (Wenatchee, Cle Elum, and Olympic). Survival rates of adult owls on the 8 Monitoring Areas generally were high, ranging from 0.85 (SE = 0.009) to 0.89 (SE = 0.010), but were declining on the Cle Elum, Olympic, and Northwestern California study areas. The meta-analysis of apparent survival indicated differences among regions and changes over time with a downward trend in the mixed-conifer and Douglas-fir regions of Washington. The meta-analysis of apparent survival also indicated that there was a negative association between fecundity and survival the following year, suggesting a cost of reproduction on survival. This effect was limited to the Douglas-fir and mixed-conifer regions of Washington and the Douglas-fir region of the Oregon Cascade Mountains. We used the reparameterized Jolly–Seber method (λRJS) to estimate annual rate of population change of territorial owls in the study areas. This estimate answers the question, Are these territorial owls being replaced in this geographically open population? Point estimates of λRJS were <1.0 for 12 of 13 study areas. The analyses provided strong evidence that populations on the Wenatchee, Cle Elum, Rainier, Olympic, Warm Springs, H. J. Andrews, Oregon Coast Ranges, and Simpson study areas were declining during the study. The mean λ̂RJS for the 13 study areas was 0.963 (SE = 0.009), suggesting that populations over all the areas were declining about 3.7% per year during the study. The mean λ̂RJS for the 8 monitoring areas for the Northwest Forest Plan was 0.976 (SE = 0.007) compared to a mean of 0.942 (SE = 0.016) for the other study areas, a 2.4-versus-5.8% decline per year. This suggested that owl populations on federal lands had higher demographic rates than elsewhere; thus, the Northwest Forest Plan appeared to have a positive effect on demography of northern spotted owls. Populations were doing poorest in Washington, where apparent survival rates and populations were declining on all 4 study areas. Our estimates of λRJS were generally lower than those reported in a previous analysis (λ̂RJS = 0.997, SE = 0.003) for many of the same areas at an earlier date. The possible causes of population declines include but are not limited to habitat loss from timber harvest and fires, competition with barred owls, and weather patterns.

Spotted owl metapopulation dynamics in Southern California

1. The California spotted owl Strix occidentalis occidentalis is found in the Sierra Nevada and in a series of isolated populations in the mountains of southern California. 2. We developed a model to assess the risk of decline of the southern California spotted owl metapopulation. We modelled the spatial structure of this metapopulation by incorporating distance-dependent dispersal and correlation among the population growth rates. 3. Demographic characteristics of the largest insular population were estimated from colour-ringing the majority of the territorial population. This owl population declined dramatically during the study period, 1987-93

PHYLOGEOGRAPHY OF SPOTTED OWL (STRIX OCCIDENTALIS) POPULATIONS BASED ON MITOCHONDRIAL DNA SEQUENCES: GENE FLOW, GENETIC STRUCTURE, AND A NOVEL BIOGEOGRAPHIC PATTERN

Mitochondrial DNA control region sequences of spotted owls (Strix occidentalis) allowed us to investigate gene flow, genetic structure, and biogeographic relationships among these forest‐dwelling birds of western North America Estimates of gene flow based on genetic partitioning and the phylogeography of haplotypes indicate substantial dispersal within three long‐recognized subspecies. However, patterns of individual phyletic relationships indicate a historical absence of gene flow among the subspecies, which are essentially monophyletic. The pattern of haplotype coalescence enabled us to identify the approximate timing and direction of a recent episode of gene flow from the Sierra Nevada to the northern coastal ranges. The three subspecies comprise phylogenetic species, and the northern spotted owl (S. o. caurina) is sister to a clade of California (S. o. occidentalis) plus Mexican spotted owls (S o lucida); this represents a novel biogeographic pattern within birds. The California spotted owl had substantially lower nucleotide diversity than the other two subspecies; this result is inconsistent with present patterns of population density A causal explanation requires postulating a severe bottleneck or a selective sweep, either of which was confined to only one geographic region.

Habitat configuration around spotted Owl sites in northwestern California

During each breeding season between 1988 and 1992, nests and daytime roosts were located for most territorial members of a contiguous population of Northern Spotted Owls (Strix occidentalis caurina) in northwestern California. Using Landsat imagery, we compared the amount of five land cover types, mature and old-growth forest fragmentation, and seral stage heterogeneity within 800 m (200 ha) circular plots around nest, roost, and random sites. This plot size was based on the observed spatial distribution of owl sites (one-half the average nearest-neighbor distance between territory centers) within the study area. Nest and roost sites were characterized by lower amounts of nonvegetated and herbaceous land cover, and greater amounts of mature and old-growth coniferous forest which was less fragmented than random sites. Mean amounts of mature and old-growth forest within 200 ha radius plots were 94.1 ha, 92.0 ha, and 71.8 for nest, roost, and random sites, respectively. The area of other land cover types was similar between owl and random sites. All habitat variables were similar at nest and roost sites. To evaluate the influence of spatial scale, habitat variables around nest and random sites also were estimated within eight concentric circular plots ranging from 800 to 3,600 m radii. Differences between nest and random sites in the amount and fragmentation of mature and old-growth forest were significant (P < 0.01) out to 1,200 m. Differences in the amount of nonvegetated and herbaceous, and seral stage heterogeneity were significant (P < 0.05) out to 1,200 m and 800 m, respectively. These results indicate that spatial scale of sampling is important and will affect analytical results. Our findings from the Klamath Physiographic Province of California were similar to results from comparable studies in Oregon and Washington.

The Invasion of Barred Owls and its Potential Effect on the Spotted Owl: a Conservation Conundrum

The spotted owl (Strix occidentalis) is a threatened species in many areas of its western North American range. Concomitant with its decline has been a rapid invasion of its range and habitat by barred owls (Strix varia), a native species that was restricted, until relatively recently, to eastern North America. We assess the theoretical potential for negative interactions between these two owls by examining size dimorphism and ecological relationships within various owl assemblages throughout the world. We then review the anecdotal, natural history, modeling, and experimental evidence that suggest barred owls may negatively affect spotted owls with at least a potential for the competitive exclusion of spotted owls by barred owls throughout all or part of the former’2019;s range. While it is widely accepted that barred owls are either causing or exacerbating declines of spotted owl populations, there are confounding factors, such as habitat loss and bad weather that also may contribute to declines of spotted owls. Both theory and empirical information suggest that barred owls are likely to have negative effects on spotted owl range and density, but the degree of the impact is not predictable. There is a conservation conundrum here, in that the barred owl is a native species that has expanded its range westwards, either naturally or with a degree of human facilitation, and now constitutes a major threat to the viability of another native species, the threatened spotted owl. We propose that only through carefully designed experiments involving removal of barred owls will we be able to determine if recent declines in spotted owl populations are caused by barred owls or by other factors. It is rare in conservation science that replicate study areas exist for which we also have long-standing demographic information, as is the case with the spotted owl. Removal experiments would take advantage of the wealth of data on spotted owls, and allow ecologists to assess formally the impacts of an invasive species on a threatened species, as well as to suggest mitigation measures.

Phylogeographic structure, gene flow and species status in blue grouse (Dendragapus obscurus)

We investigated the genetic population structure and species status of a relatively sedentary bird that is a permanent resident of western North American forests, the blue grouse (Dendragapus obscurus). Phylogenetic analysis of complete mitochondrial control region DNA sequences resulted in the identification of three basal clades of haplotypes that were largely congruent with well‐known biogeographical regions. These clades corresponded to the parapatric sooty (D. o. fuliginosus) and dusky (D. o. obscurus) subspecies groups of blue grouse plus a previously unrecognized division between northern and southern dusky grouse populations; the latter does not correspond closely to any currently recognized subspecies boundary. Approximately 66% of the total genetic variation was distributed among these three regions. Maximum likelihood estimates of gene flow between the regions were low or asymmetric; gene flow has been insufficient to prevent genetic divergence between dusky and sooty grouse. Estimates of gene flow among populations within sooty grouse were large except across the Columbia River valley. Among populations of dusky grouse, estimates of gene flow were heterogeneous and asymmetrical, reflecting large‐scale fragmentation of the distribution due to landscape features and associated vegetation. Genetic, morphological and behavioural evidence suggest that sooty and dusky grouse are species‐level taxa; the specific status of a third clade remains ambiguous.

Genetic structure, introgression, and a narrow hybrid zone between northern and California spotted owls (Strix occidentalis)

The northern spotted owl (Strix occidentalis caurina) is a threatened subspecies and the California spotted owl (Strix occidentalis occidentalis) is a subspecies of special concern in the western United States. Concern for their continued viability has arisen because of habitat loss caused by timber harvesting. The taxonomic status of the northern subspecies has been the subject of continuing controversy. We investigated the phylogeographical and population genetic structure of northern and California spotted owls with special reference to their region of contact. Mitochondrial DNA (mtDNA) control region sequences confirmed the existence of two well‐differentiated lineages connected by a narrow hybrid zone in a region of low population density in north central California. Maximum‐likelihood estimates indicated bidirectional gene flow between the lineages but limited introgression outside the region of contact. The lengths of both the mtDNA hybrid zone and the reduced density patch were similar and slightly exceeded estimates of natal dispersal distances. This suggests that the two subspecies were in secondary contact in a hybrid zone trapped by a population density trough. Consequently, the zone of interaction is expected to be geographically stable. We discovered a third, rare clade of haplotypes, which we interpreted to be a result of incomplete lineage sorting; those haplotypes result in a paraphyletic northern spotted owl with respect to the California spotted owl. A congeneric species, the barred owl (Strix varia), occasionally hybridizes with spotted owls; our results indicated an upper bound for the frequency of barred owl mtDNA haplotypes in northern spotted owl populations of 3%.